The mechanism of a repression of translational initiation in cultured human cells exposed to deprivation of essential amino acids is being investigated. Both in vitro and in vivo experiments will be performed to identify and characterize the biochemical species concerned with this repression. The synthesis of mRNA coding for ribosomal proteins in growing, cultured human cells exposed to growth stress is to be examined, by using a cell-free protein synthesis system from wheat germ to translate the mRNA population extracted from the human cells. Two-dimensional gel electrophoresis will be used to resolve and identify the products produced in the wheat germ system. BIBLIOGRAPHIC REFERENCES: Porchhammer, J., Nexo, B., and Vaughan, M.H., "Cellular Pools of Viral Proteins in 3T3 Cells Chronically Infected with Maloney Murine Leukemia Virus", Virology, 71, 134 (1976). Bolcsfoldi, G., Ritter, E., and Vaughan, M.H., "Highly Charged Radioactive Initiator Methionyl Transfer RNA from In Vivo Labeled HeLa Cells", Anal. Biochem., 74, 521 (1976).